The present invention pertains to a device and method for introducing an etching gas into the reaction chamber of a dry etching apparatus.
In dry etching apparatus, the etching gas is ionized by electrons flowing between two or more electrodes to form a plasma. It is this plasma which then etches a workpiece. It is desirable for this etching to be done in a uniform manner over the entire workpiece.
In the prior art, one of the techniques used in attempting to obtain a uniform etch is to introduce the etching gas in a uniform manner. This is accomplished by the use of a plurality of small uniform inlet holes which introduce a constant flow of etching gas into a reaction chamber as shown in U.S. Pat. No. 4,534,816 entitled "Single Wafer Plasma Etch Reactor", issued Aug. 13, 1985. This, along with other prior art, utilize a plurality of small uniform inlet holes to introduce an etching gas uniformly. Other devices such as trumpet-shaped or split gas inlets introduce the gas uniformly through larger openings. The prior art strives to introduce the gas over a uniform area so that a uniform plasma glow will be established, which is then capable of etching the workpiece in a uniform manner.
The problem with this prior art is that the gas might be introduced uniformly, but other characteristics of the dry etching apparatus are non-uniform. Thus, the resulting etch, as in the trumpet-shaped gas inlet, which commonly results in a doughnut clearing pattern, is non-uniform.